Activity Analysis

Each day when I wake up I eat breakfast, usually cereal. My right arm starts in a relaxed extended position down by my side. To eat the cereal, I start by performing shoulder flexion until my arm sticks straight out in front of me. I extend my right arm out at the elbow joint to grab the spoon and flex my fingers around the spoon to hold it. Then, I flex my arm while also medially rotating my arm to bring the spoon to the bowl. I slightly extend my wrist in order to scoop the cereal out of the bowl. I then flex my arm even more to get the spoon to my mouth. The motions of flexion and extension at the elbow joint occur in the sagittal plane around the frontal axis. The osteokinematics of the elbow joint are extension to flexion in an open kinematic chain. In regards to arthrokinematics, the concave ulna is the moving segment when decreasing the angle between the humerus and the ulna. The concave ulnar surface rolls and glides anteriorly on the convex surface of the humerus. The prime mover for elbow flexion is the biceps brachii, which performs a concentric contraction.